/*
 * FreeRTOS Kernel V10.3.0
 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * http://www.FreeRTOS.org
 * http://aws.amazon.com/freertos
 *
 * 1 tab == 4 spaces!
 */

/*
 * Creates two sets of two tasks.  The tasks within a set share a variable, access
 * to which is guarded by a semaphore.
 *
 * Each task starts by attempting to obtain the semaphore.  On obtaining a
 * semaphore a task checks to ensure that the guarded variable has an expected
 * value.  It then clears the variable to zero before counting it back up to the
 * expected value in increments of 1.  After each increment the variable is checked
 * to ensure it contains the value to which it was just set. When the starting
 * value is again reached the task releases the semaphore giving the other task in
 * the set a chance to do exactly the same thing.  The starting value is high
 * enough to ensure that a tick is likely to occur during the incrementing loop.
 *
 * An error is flagged if at any time during the process a shared variable is
 * found to have a value other than that expected.  Such an occurrence would
 * suggest an error in the mutual exclusion mechanism by which access to the
 * variable is restricted.
 *
 * The first set of two tasks poll their semaphore.  The second set use blocking
 * calls.
 *
 */

#include <stdlib.h>

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"
#include "semphr.h"

/* Demo app include files. */
#include "semtest.h"

/* The value to which the shared variables are counted. */
#define semtstBLOCKING_EXPECTED_VALUE ((uint32_t)0xfff)
#define semtstNON_BLOCKING_EXPECTED_VALUE ((uint32_t)0xff)

#define semtstSTACK_SIZE configMINIMAL_STACK_SIZE

#define semtstNUM_TASKS (4)

#define semtstDELAY_FACTOR ((TickType_t)10)

/* The task function as described at the top of the file. */
static portTASK_FUNCTION_PROTO(prvSemaphoreTest, pvParameters);

/* Structure used to pass parameters to each task. */
typedef struct SEMAPHORE_PARAMETERS {
	SemaphoreHandle_t xSemaphore;
	volatile uint32_t *pulSharedVariable;
	TickType_t xBlockTime;
} xSemaphoreParameters;

/* Variables used to check that all the tasks are still running without errors. */
static volatile short sCheckVariables[semtstNUM_TASKS] = { 0 };
static volatile short sNextCheckVariable = 0;

/*-----------------------------------------------------------*/

void vStartSemaphoreTasks(UBaseType_t uxPriority)
{
	xSemaphoreParameters *pxFirstSemaphoreParameters,
		*pxSecondSemaphoreParameters;
	const TickType_t xBlockTime = (TickType_t)100;

	/* Create the structure used to pass parameters to the first two tasks. */
	pxFirstSemaphoreParameters = (xSemaphoreParameters *)pvPortMalloc(
		sizeof(xSemaphoreParameters));

	if (pxFirstSemaphoreParameters != NULL) {
		/* Create the semaphore used by the first two tasks. */
		pxFirstSemaphoreParameters->xSemaphore =
			xSemaphoreCreateBinary();

		if (pxFirstSemaphoreParameters->xSemaphore != NULL) {
			xSemaphoreGive(pxFirstSemaphoreParameters->xSemaphore);

			/* Create the variable which is to be shared by the first two tasks. */
			pxFirstSemaphoreParameters->pulSharedVariable =
				(uint32_t *)pvPortMalloc(sizeof(uint32_t));

			/* Initialise the share variable to the value the tasks expect. */
			*(pxFirstSemaphoreParameters->pulSharedVariable) =
				semtstNON_BLOCKING_EXPECTED_VALUE;

			/* The first two tasks do not block on semaphore calls. */
			pxFirstSemaphoreParameters->xBlockTime = (TickType_t)0;

			/* Spawn the first two tasks.  As they poll they operate at the idle priority. */
			xTaskCreate(prvSemaphoreTest, "PolSEM1",
				    semtstSTACK_SIZE,
				    (void *)pxFirstSemaphoreParameters,
				    tskIDLE_PRIORITY, (TaskHandle_t *)NULL);
			xTaskCreate(prvSemaphoreTest, "PolSEM2",
				    semtstSTACK_SIZE,
				    (void *)pxFirstSemaphoreParameters,
				    tskIDLE_PRIORITY, (TaskHandle_t *)NULL);

			/* vQueueAddToRegistry() adds the semaphore to the registry, if one
			is in use.  The registry is provided as a means for kernel aware
			debuggers to locate semaphores and has no purpose if a kernel aware
			debugger is not being used.  The call to vQueueAddToRegistry() will
			be removed by the pre-processor if configQUEUE_REGISTRY_SIZE is not
			defined or is defined to be less than 1. */
			vQueueAddToRegistry(
				(QueueHandle_t)
					pxFirstSemaphoreParameters->xSemaphore,
				"Counting_Sem_1");
		}
	}

	/* Do exactly the same to create the second set of tasks, only this time
	provide a block time for the semaphore calls. */
	pxSecondSemaphoreParameters = (xSemaphoreParameters *)pvPortMalloc(
		sizeof(xSemaphoreParameters));
	if (pxSecondSemaphoreParameters != NULL) {
		pxSecondSemaphoreParameters->xSemaphore =
			xSemaphoreCreateBinary();

		if (pxSecondSemaphoreParameters->xSemaphore != NULL) {
			xSemaphoreGive(pxSecondSemaphoreParameters->xSemaphore);

			pxSecondSemaphoreParameters->pulSharedVariable =
				(uint32_t *)pvPortMalloc(sizeof(uint32_t));
			*(pxSecondSemaphoreParameters->pulSharedVariable) =
				semtstBLOCKING_EXPECTED_VALUE;
			pxSecondSemaphoreParameters->xBlockTime =
				xBlockTime / portTICK_PERIOD_MS;

			xTaskCreate(prvSemaphoreTest, "BlkSEM1",
				    semtstSTACK_SIZE,
				    (void *)pxSecondSemaphoreParameters,
				    uxPriority, (TaskHandle_t *)NULL);
			xTaskCreate(prvSemaphoreTest, "BlkSEM2",
				    semtstSTACK_SIZE,
				    (void *)pxSecondSemaphoreParameters,
				    uxPriority, (TaskHandle_t *)NULL);

			/* vQueueAddToRegistry() adds the semaphore to the registry, if one
			is in use.  The registry is provided as a means for kernel aware
			debuggers to locate semaphores and has no purpose if a kernel aware
			debugger is not being used.  The call to vQueueAddToRegistry() will
			be removed by the pre-processor if configQUEUE_REGISTRY_SIZE is not
			defined or is defined to be less than 1. */
			vQueueAddToRegistry(
				(QueueHandle_t)
					pxSecondSemaphoreParameters->xSemaphore,
				"Counting_Sem_2");
		}
	}
}
/*-----------------------------------------------------------*/

static portTASK_FUNCTION(prvSemaphoreTest, pvParameters)
{
	xSemaphoreParameters *pxParameters;
	volatile uint32_t *pulSharedVariable, ulExpectedValue;
	uint32_t ulCounter;
	short sError = pdFALSE, sCheckVariableToUse;

	/* See which check variable to use.  sNextCheckVariable is not semaphore
	protected! */
	portENTER_CRITICAL();
	sCheckVariableToUse = sNextCheckVariable;
	sNextCheckVariable++;
	portEXIT_CRITICAL();

	/* A structure is passed in as the parameter.  This contains the shared
	variable being guarded. */
	pxParameters = (xSemaphoreParameters *)pvParameters;
	pulSharedVariable = pxParameters->pulSharedVariable;

	/* If we are blocking we use a much higher count to ensure loads of context
	switches occur during the count. */
	if (pxParameters->xBlockTime > (TickType_t)0) {
		ulExpectedValue = semtstBLOCKING_EXPECTED_VALUE;
	} else {
		ulExpectedValue = semtstNON_BLOCKING_EXPECTED_VALUE;
	}

	for (;;) {
		/* Try to obtain the semaphore. */
		if (xSemaphoreTake(pxParameters->xSemaphore,
				   pxParameters->xBlockTime) == pdPASS) {
			/* We have the semaphore and so expect any other tasks using the
			shared variable to have left it in the state we expect to find
			it. */
			if (*pulSharedVariable != ulExpectedValue) {
				sError = pdTRUE;
			}

			/* Clear the variable, then count it back up to the expected value
			before releasing the semaphore.  Would expect a context switch or
			two during this time. */
			for (ulCounter = (uint32_t)0;
			     ulCounter <= ulExpectedValue; ulCounter++) {
				*pulSharedVariable = ulCounter;
				if (*pulSharedVariable != ulCounter) {
					sError = pdTRUE;
				}
			}

			/* Release the semaphore, and if no errors have occurred increment the check
			variable. */
			if (xSemaphoreGive(pxParameters->xSemaphore) ==
			    pdFALSE) {
				sError = pdTRUE;
			}

			if (sError == pdFALSE) {
				if (sCheckVariableToUse < semtstNUM_TASKS) {
					(sCheckVariables[sCheckVariableToUse])++;
				}
			}

			/* If we have a block time then we are running at a priority higher
			than the idle priority.  This task takes a long time to complete
			a cycle	(deliberately so to test the guarding) so will be starving
			out lower priority tasks.  Block for some time to allow give lower
			priority tasks some processor time. */
			vTaskDelay(pxParameters->xBlockTime *
				   semtstDELAY_FACTOR);
		} else {
			if (pxParameters->xBlockTime == (TickType_t)0) {
				/* We have not got the semaphore yet, so no point using the
				processor.  We are not blocking when attempting to obtain the
				semaphore. */
				taskYIELD();
			}
		}
	}
}
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running. */
BaseType_t xAreSemaphoreTasksStillRunning(void)
{
	static short sLastCheckVariables[semtstNUM_TASKS] = { 0 };
	BaseType_t xTask, xReturn = pdTRUE;

	for (xTask = 0; xTask < semtstNUM_TASKS; xTask++) {
		if (sLastCheckVariables[xTask] == sCheckVariables[xTask]) {
			xReturn = pdFALSE;
		}

		sLastCheckVariables[xTask] = sCheckVariables[xTask];
	}

	return xReturn;
}
